The 24-hour period during which the earth completes one rotation on its axis.
As it relates to the sun. Without Sol, how would you know when you completed the rotation?
Isn’t that like saying without a microscope how would you know there are bacteria?
Bacteria exist irrespective of their detection by the microscope. Also, even a complete nonscientific mind can think of ways to detect and observe the rotation of the earth without the presence of the sun.
"Also, even a complete nonscientific mind can think of ways to detect and observe the rotation of the earth without the presence of the sun."
Yet, none of these 'ways' were in place on days 1 and 2 of Creation.